Historically intraoral dental radiography has been based on X-ray film. Since the film is used only once, there is no need for re-sterilization after use.
Recently, however, the dental field is moving toward digital radiography systems with reusable image receivers, such as Photostimulable Phosphor (PSP) plates. A PSP plate is inserted in the patient's mouth and exposed to X-rays, like a standard film. The exposed plate is removed from the mouth and "developed" by a laser scanner, whereupon the image on the plate is displayed and stored by a computer. The plate is then erased, by a flash of bright light, and is ready for reuse.
With the advent of reusable image receivers, complications have emerged concerning the sterilization and maintenance of the reusable media. PSP plates are degraded by both the chemicals and heat that can be used to sterilize them between uses. Therefore, the plate must be sealed inside a suitable envelope before it is placed in the mouth. A special procedure must be followed to remove the plate from the envelope for development, in order not to compromise the plate's sterility.